This proposal is concerned with the analysis of the relationships between ionic concentration gradients, transmembrane ionic movements, and ionic active transport processes in conjunction with elucidating the metabolic processes which support these activities in the photoreceptor cell of the mammalian retina. Measurements of electrical and metabolic activities are made with respect to altered intracellular and extracellular ionic concentrations, changes in the state of adaptation, and different levels of glucose and oxygen availability. The role of calcium in these processes is studied under conditions which promote a rise in its intracellular concentration. With the use of specific oxidizing chemicals, the effects of altering the concentration of reduced and oxidized glutathione on retinal function is studied. The dependence of photoreceptor cell function on the levels of cyclic GMP and cyclic AMP is investigated following impairment in those systems controlling their synthesis or degradation. The role of potassium in the generation of retinal potentials is studied with ion specific microelectrodes. Metabolic parameters to be measured include lactate production, oxygen consumption, ATPase activities, ATP concentration, glutathione levels, and the concentrations of cyclic nucleotides. Light-induced electrical activities are recorded intraretinally with microelectrodes in superfused retinas from rat and rabbit.